In electrostatic copying processes, a latent electrostatic image formed on an element is developed into a visible image with toner particles.
So called dry or particulate toner powders can be prepared by a variety of techniques. In one process, a water-immiscible polymerizable liquid monomer and colorant (i.e., pigment or dye) are dispersed as droplets in an aqueous medium containing a colloidally sized suspending agent. The monomer is polymerized to form solid colorant containing polymeric particles that are separated and dried. The process is useful in making very small particle size toner powders (under about 10 microns) that can be employed in making high resolution developed toned images. The limited coalescence process is described, for example, in U.S. Pat. No. 3,615,972.
Another example is an evaporation limited coalescence process, where the stabilizer used is also a colloidal silica, or the like, and where the suspended small droplets comprise a solution of polymer in a non-aqueous, water immiscible solvent liquid. The solvent is removed and the particles are separated, washed and dried. Such a process is disclosed in U.S. Pat. No. 4,833,060.
A further example is a limited coalescence polymerization process wherein the stabilizer used is an emulsion polymerized aqueous latex of certain copolymers containing oleophilic and hydrophilic combined monomers as is disclosed in published European Patent Application No. 0 334 126.